This study was carried out to determine the effect of beta-carotene on ovarian function and pregnancy rates in repeat breeder cows. Twenty-six repeat breeder Holstein cows were randomly assigned into control (n=11) and carotene (n=15) groups. Cows were fed with diet in the form of total mixed ration (39.80% neutral detergent fiber and 16.20% crude protein of dry matter). Treatment cows received an intramuscular injection of beta-carotene (1 mg/kg) simultaneously with the first GnRH injection. Largest follicle (P<0.05) and corpus luteum diameters (P<0.01) together with serum progesterone (P<0.01), beta-carotene (P<0.05) and vitamin A (P<0.01) levels were all significantly higher in the carotene group on the day of PGF2 alpha injection. At the second GnRH injection, largest follicle diameter (P<0.01), serum estradiol (P<0.01), beta-carotene (P<0.01), and vitamin A (P<0.01) levels were again higher in the carotene group. Serum estradiol (P<0.01) and beta-carotene (P<0.05) levels were still significantly higher in the carotene group at the time of Al. Ovulation response did not differ between groups after both first and second GnRH injection. The pregnancy rate was 27.2% in the control group, and 33.3% in the carotene group but this difference was not statistically significant. In conclusion, it was Suggested that beta-carotene did not have any significant effects on ovulation or pregnancy rates in ovsynch-treated repeat breeder cows; however it increased serum estradiol and progesterone levels due to increased follicle size and corpus luteum functionality, respectively.